11,911 research outputs found

    Quantum Mechanics Lecture Notes. Selected Chapters

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    These are extended lecture notes of the quantum mechanics course which I am teaching in the Weizmann Institute of Science graduate physics program. They cover the topics listed below. The first four chapter are posted here. Their content is detailed on the next page. The other chapters are planned to be added in the coming months. 1. Motion in External Electromagnetic Field. Gauge Fields in Quantum Mechanics. 2. Quantum Mechanics of Electromagnetic Field 3. Photon-Matter Interactions 4. Quantization of the Schr\"odinger Field (The Second Quantization) 5. Open Systems. Density Matrix 6. Adiabatic Theory. The Berry Phase. The Born-Oppenheimer Approximation 7. Mean Field Approaches for Many Body Systems -- Fermions and Boson

    Constraining a Model of the Radio Sky Below 6 MHz Using the Parker Solar Probe/FIELDS Instrument in Preparation for Upcoming Lunar-based Experiments

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    We present a Bayesian analysis of data from the FIELDS instrument on board the Parker Solar Probe (PSP) spacecraft with the aim of constraining low frequency (\lesssim 6 MHz) sky in preparation for several upcoming lunar-based experiments. We utilize data recorded during PSP's ``coning roll'' maneuvers, in which the axis of the spacecraft is pointed 45^{\circ} off of the Sun. The spacecraft then rotates about a line between the Sun and the spacecraft with a period of 24 minutes. We reduce the data into two formats: roll-averaged, in which the spectra are averaged over the roll, and phase-binned, in which the spectra are binned according to the phase of the roll. We construct a forward model of the FIELDS observations that includes numerical simulations of the antenna beam, an analytic emissivity function of the galaxy, and estimates of the absorption due to free electrons. Fitting 5 parameters, we find that the roll-averaged data can be fit well by this model and we obtain posterior parameter constraints that are in general agreement with previous estimates. The model is not, however, able to fit the phase-binned data well, likely due to limitations such as the lack of non-smooth emission structure at both small and large scales, enforced symmetry between the northern and southern galactic hemispheres, and large uncertainties in the free electron density. This suggests that significant improvement in the low frequency sky model is needed in order to fully and accurately represent the sky at frequencies below 6 MHz.Comment: 18 pages, 10 figures, 5 tables. Under review in the Astrophysical Journa

    Modelling uncertainties for measurements of the H → γγ Channel with the ATLAS Detector at the LHC

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    The Higgs boson to diphoton (H → γγ) branching ratio is only 0.227 %, but this final state has yielded some of the most precise measurements of the particle. As measurements of the Higgs boson become increasingly precise, greater import is placed on the factors that constitute the uncertainty. Reducing the effects of these uncertainties requires an understanding of their causes. The research presented in this thesis aims to illuminate how uncertainties on simulation modelling are determined and proffers novel techniques in deriving them. The upgrade of the FastCaloSim tool is described, used for simulating events in the ATLAS calorimeter at a rate far exceeding the nominal detector simulation, Geant4. The integration of a method that allows the toolbox to emulate the accordion geometry of the liquid argon calorimeters is detailed. This tool allows for the production of larger samples while using significantly fewer computing resources. A measurement of the total Higgs boson production cross-section multiplied by the diphoton branching ratio (σ × Bγγ) is presented, where this value was determined to be (σ × Bγγ)obs = 127 ± 7 (stat.) ± 7 (syst.) fb, within agreement with the Standard Model prediction. The signal and background shape modelling is described, and the contribution of the background modelling uncertainty to the total uncertainty ranges from 18–2.4 %, depending on the Higgs boson production mechanism. A method for estimating the number of events in a Monte Carlo background sample required to model the shape is detailed. It was found that the size of the nominal γγ background events sample required a multiplicative increase by a factor of 3.60 to adequately model the background with a confidence level of 68 %, or a factor of 7.20 for a confidence level of 95 %. Based on this estimate, 0.5 billion additional simulated events were produced, substantially reducing the background modelling uncertainty. A technique is detailed for emulating the effects of Monte Carlo event generator differences using multivariate reweighting. The technique is used to estimate the event generator uncertainty on the signal modelling of tHqb events, improving the reliability of estimating the tHqb production cross-section. Then this multivariate reweighting technique is used to estimate the generator modelling uncertainties on background V γγ samples for the first time. The estimated uncertainties were found to be covered by the currently assumed background modelling uncertainty

    TOWARDS AN UNDERSTANDING OF EFFORTFUL FUNDRAISING EXPERIENCES: USING INTERPRETATIVE PHENOMENOLOGICAL ANALYSIS IN FUNDRAISING RESEARCH

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    Physical-activity oriented community fundraising has experienced an exponential growth in popularity over the past 15 years. The aim of this study was to explore the value of effortful fundraising experiences, from the point of view of participants, and explore the impact that these experiences have on people’s lives. This study used an IPA approach to interview 23 individuals, recognising the role of participants as proxy (nonprofessional) fundraisers for charitable organisations, and the unique organisation donor dynamic that this creates. It also bought together relevant psychological theory related to physical activity fundraising experiences (through a narrative literature review) and used primary interview data to substantiate these. Effortful fundraising experiences are examined in detail to understand their significance to participants, and how such experiences influence their connection with a charity or cause. This was done with an idiographic focus at first, before examining convergences and divergences across the sample. This study found that effortful fundraising experiences can have a profound positive impact upon community fundraisers in both the short and the long term. Additionally, it found that these experiences can be opportunities for charitable organisations to create lasting meaningful relationships with participants, and foster mutually beneficial lifetime relationships with them. Further research is needed to test specific psychological theory in this context, including self-esteem theory, self determination theory, and the martyrdom effect (among others)

    Compatibility and challenges in machine learning approach for structural crack assessment

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    Structural health monitoring and assessment (SHMA) is exceptionally essential for preserving and sustaining any mechanical structure’s service life. A successful assessment should provide reliable and resolute information to maintain the continuous performance of the structure. This information can effectively determine crack progression and its overall impact on the structural operation. However, the available sensing techniques and methods for performing SHMA generate raw measurements that require significant data processing before making any valuable predictions. Machine learning (ML) algorithms (supervised and unsupervised learning) have been extensively used for such data processing. These algorithms extract damage-sensitive features from the raw data to identify structural conditions and performance. As per the available published literature, the extraction of these features has been quite random and used by academic researchers without a suitability justification. In this paper, a comprehensive literature review is performed to emphasise the influence of damage-sensitive features on ML algorithms. The selection and suitability of these features are critically reviewed while processing raw data obtained from different materials (metals, composites and polymers). It has been found that an accurate crack prediction is only possible if the selection of damage-sensitive features and ML algorithms is performed based on available raw data and structure material type. This paper also highlights the current challenges and limitations during the mentioned sections

    A Molecular Approach to the Diagnosis, Assessment, Monitoring and Treatment of Pulmonary Non-Tuberculous Mycobacterial Disease

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    Introduction: Non-Tuberculous Mycobacteria (NTM) can cause disease of the lungs and sinuses, lymph nodes, joints and central nervous system as well as disseminated infections in immunocompromised individuals. Efforts to tackle infections in NTM are hampered by a lack of reliable biomarkers for diagnosis, assessment of disease activity, and prognostication. Aims: The broad aims of this thesis are: 1. to develop molecular assays capable of quantifying the 6 most common pathogenic mycobacteria (M. abscessus, M. avium, M. intracellulare, M. malmoense, M. kansasii, M. xenopi) and calculate comparative sensitivities and specificities for each assay. 2. to assess patients’ clinical course over 12 – 18 months by performing the developed molecular assays against DNA extracted from sputum from patients with NTM infection. 3. to assess dynamic bacterial changes of the lung microbiome in patients on treatment for NTM disease and those who are treatment na ve. Methods: DNA was extracted from a total of 410 sputum samples obtained from 38 patients who were either: • commencing treatment for either M. abscessus or Mycobacterium avium complex. • considered colonised with M. abscessus or Mycobacterium avium complex (i.e. cultured NTM but were not deemed to have infection as they did not meet ATS or BTS criteria for disease). • Diagnosed with cystic fibrosis (CF) or non-CF bronchiectasis but had never cultured NTM. For the development of quantitative molecular assays, NTM hsp65 gene sequences were aligned and interrogated for areas of variability. These variable regions enabled the creation of species specific probes. In vitro sensitivity and specificity for each probe was determined by testing each probe against a panel of plasmids containing hsp65 gene inserts from different NTM species. Quantification accuracy was determined by using each assay against a mock community containing serial dilutions of target DNA. Each sample was tested with the probes targeting: M. abscessus, M. avium and M. intracellulare producing a longitudinal assessment of NTM copy number during each patient’s clinical course. In addition, a total of 64 samples from 16 patients underwent 16S rRNA gene sequencing to characterise longitudinal changes in the microbiome of both NTM disease and controls. Results: In vitro sensitivity for the custom assays were 100% and specificity ranged from 91.6% to 100%. In terms of quantification accuracy, there was no significant difference between the measured results of each assay and the expected values when performed in singleplex. The assays were able to accurately determine NTM copy number to a theoretical limit of 10 copies/μl. When used against samples derived from human sputum and using culture results as a gold standard, the sensitivity of the assay for M. abscessus was found to be 0.87 and 0.86 for MAC. The specificity of the assay for M. abscessus was 0.95 and 0.62 for MAC. The negative predictive value of the assay for M. abscessus was 0.98 and 0.95 for MAC. This resulted in an AUC of 0.92 for M. abscessus and 0.74 for MAC. Longitudinal analysis of the lung microbiome using 16SrRNA gene sequencing showed that bacterial burden initially decreases after initiation of antibiotic therapy but begins to return to normal levels over several months of antibiotic therapy. This effect is mirrored by changes in alpha diversity. The decrease in bacterial burden and loss of alpha diversity was found to be secondary to significant changes in specific genera such as Veillonella and Streptococcus. The abundance of other Proteobacteria such as Pseudomonas remain relatively constant. Conclusion: The molecular assay has shown high in vitro sensitivity and specificity for the detection and accurate quantification of the 6 most commonly pathogenic NTM species. The assays successfully identified NTM DNA from human sputum samples. A notable association between NTM copy number and the cessation of one or more antibiotics existed (i.e. when one antibiotic was stopped because of patient intolerance, NTM copy number increased, often having been unrecordable prior to this). The qPCR assays developed in this thesis provide an affordable, real time and rapid measurement of NTM burden allowing clinicians to act on problematic results sooner than currently possible. There was no significant difference between the microbiome in bronchiectasis and cystic fibrosis nor was there a significant difference between the microbiome in patients requiring treatment for NTM and those who did not. Patients receiving treatment experienced an initial decrease in bacterial burden over the first weeks of treatment followed by a gradual increase towards baseline over the next weeks to months. This change was mirrored in measures of alpha diversity. Changes in abundance and diversity were accounted for by decreases in specific bacteria whilst the abundance of other bacteria increased, occupying the microbial niche created. These bacteria (for example Pseudomonas spp) are often associated with morbidity.Open Acces

    Growth trends and site productivity in boreal forests under management and environmental change: insights from long-term surveys and experiments in Sweden

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    Under a changing climate, current tree and stand growth information is indispensable to the carbon sink strength of boreal forests. Important questions regarding tree growth are to what extent have management and environmental change influenced it, and how it might respond in the future. In this thesis, results from five studies (Papers I-V) covering growth trends, site productivity, heterogeneity in managed forests and potentials for carbon storage in forests and harvested wood products via differing management strategies are presented. The studies were based on observations from national forest inventories and long-term experiments in Sweden. The annual height growth of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) had increased, especially after the millennium shift, while the basal area growth remains stable during the last 40 years (Papers I-II). A positive response on height growth with increasing temperature was observed. The results generally imply a changing growing condition and stand composition. In Paper III, yield capacity of conifers was analysed and compared with existing functions. The results showed that there is a bias in site productivity estimates and the new functions give better prediction of the yield capacity in Sweden. In Paper IV, the variability in stand composition was modelled as indices of heterogeneity to calibrate the relationship between basal area and leaf area index in managed stands of Norway spruce and Scots pine. The results obtained show that the stand structural heterogeneity effects here are of such a magnitude that they cannot be neglected in the implementation of hybrid growth models, especially those based on light interception and light-use efficiency. In the long-term, the net climate benefits in Swedish forests may be maximized through active forest management with high harvest levels and efficient product utilization, compared to increasing carbon storage in standing forests through land set-asides for nature conservation (Paper V). In conclusion, this thesis offers support for the development of evidence-based policy recommendations for site-adapted and sustainable management of Swedish forests in a changing climate

    Understanding novel EGFP-Ubx protein-based film formation

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    Protein-based materials are currently the subject of intense research interest since they have an extended range of potential applications, such as im-proved bio-membrane biocompatibility for implanted medical devices and the creation of platform materials for novel biosensors. Monomers from Ultrabithorax (Ubx) transcription factor are known to spontaneously self-assemble at an air-water interface to form a monolayer, which has then been used as a basis for forming biopolymeric ˝bers. Here we used the Lang-muir trough technique, Brewster angle microscopy (BAM), ellipsometry and neutron re˛ectometry (NR) to investigate the in˛uences of di˙erent exper-imental conditions on EGFP-Ubx monolayer formation and the impact on biopolymeric ˝ber structure. We varied protein concentration, bu˙er prop-erties and waiting times prior to forming biopolymeric ˝bers. Interestingly, we found 3 phases of material formation which brought us to a new protocol for forming ˝bers that reduced protein concentration by 5-fold and wait-ing times by 100-fold. Moreover, an in-house developed MATLAB code was used to analyze SEM images and obtain quantitative structural information about the biopolymeric ˝bers that were correlated directly to the surface ˝lm characteristics measured in the LB trough. These new insights into ˝ber formation and structure enhance the usefulness of the Ubx-based biopolymer for biomedical applications

    Astrometry in two-photon interferometry using Earth rotation fringe scan

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    Optical interferometers may not require a phase-stable optical link between the stations if instead sources of quantum-mechanically entangled pairs could be provided to them, enabling long baselines. We developed a new variation of this idea, proposing that photons from two different astronomical sources could be interfered at two decoupled stations. Interference products can then be calculated in post-processing or requiring only a slow, classical connection between stations. In this work, we investigated practical feasibility of this approach. We developed a Bayesian analysis method for the earth rotation fringe scanning technique and showed that in the limit of high signal-to-noise ratio it reproduced the results from a simple Fisher matrix analysis. We identify candidate stair pairs in the northern hemisphere, where this technique could be applied. With two telescopes with an effective collecting area of 2\sim 2 m2^2, we could detect fringing and measure the astrometric separation of the sources at 10μ\sim 10\,\muas precision in a few hours of observations, in agreement with previous estimates
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